In vehicles equipped with a driver air bag assembly, the air bag assembly is typically included in a steering wheel hub module including the air bag assembly and a hub cover designed to open upon deployment of the air bag. Typically, the hub module is suspended on an armature base plate of the steering wheel armature by four telescoping spring-biased corner posts, which incorporate horn actuation switch contacts or terminals. Depressing the air bag module by applying an actuation force against the hub cover compresses one or more of the springs to make contact with one or more switch terminals to actuate the horn. The actuation force required to make contact with at least one of the switch terminals may also be referred to as the horn effort, and is defined by the condition of the spring. The springs of the spring-biased actuation system can be affected by loads imposed on the springs by the gravitational force resulting from the weight of the hub module and the location of the center of gravity of the hub module relative to the spring placement, which may increase the relative load on one or more of the springs. Over time, the spring force, and the corresponding actuation force and horn effort, can change due to wear and/or fatigue caused by the gravitational loads, such that the horn effort required to actuate the horn may vary from location to location on the actuation surface, e.g., on the hub cover, and from one spring post and/or switch terminal to another. Sagging of the hub module relative to the armature base, due to gravitational loads, may decrease the effort required to actuate the horn in some locations on the hub cover, increasing susceptibility to unintentional actuation of the horn caused by incidental input to those locations, or unintended terminal contact due to incidental hub module movement or vibration during vehicle use.